EtherChannel Manual Configuration

An EtherChannel is a group of links that work together as a single link. There are two ways to configure an EtherChannel: Static and Dynamic. In the static method, you manually configure an EtherChannel. In the Dynamic method, you configure an EtherChannel protocol. The EtherChannel protocol configures and manages the EtherChannel. This tutorial explains the static (manual) method of EtherChannel configuration.

Manual EtherChannel Configuration

The following interface configuration mode command creates a new EtherChannel if one with the specified number does not exist, and adds the interface to the EtherChannel. If an EtherChannel with the specified number exists, it adds the interface to the EtherChannel.

Switch(config-if)#channel-group [number] mode on

You must run the above command on all interfaces you want to add to the EtherChannel.

EtherChannel Packet Tracer Example

Create a Packet Tracer lab as shown in the following image, or download the following pre-built lab and open it in Packet Tracer.

Download Packet Tracer Lab

STP (Snapping Tree Protocol)

STP automatically detects loops and blocks ports that cause them in Cisco switches.

You can verify it by viewing the STP port states. The show spanning-tree command displays the STP port states.

As shown above, STP blocked F0/2, F0/3, and F0/4 ports to prevent loops. Since STP has blocked these ports, the switch cannot use them to forward frames. Access the interface configuration mode of F0/1, F0/2, F0/3, and F0/4 interfaces and run the following command.

Switch(config-if)#channel-group 1 mode on

You can use any channel number between 1 and 6. The channel number must be the same across all interfaces you want to put in a channel group. You can add up to eight ports to a single EtherChannel.

Use the show spanning-tree command again to view the STP ports' states.

As shown in the output above, there is only one interface instead of four. It is a pool of all four interfaces. STP treats this pool as a single interface. If any interface from this pool fails, it does not trigger STP. STP reruns its algorithm only when all interfaces inside the pool fail.

On a physical Cisco switch or any advanced simulator software such as GSN3, you can use the show etherchannel [number] summary command to view detailed information about the specified EtherChannel. Packet Tracer supports a stripped-down version of this command.

The following image shows the output of the show spanning-tree command on the second switch.

The following image shows the configuration steps for the EtherChannel on the second switch.

The following image shows the output of the show spanning-tree command on the second switch after the EtherChannel Configuration.

Download the packet tracer lab with the configuration

Conclusion

An EtherChannel is a group of ports that works as a single port on the switch. You can use EtherChannels for various reasons. The two most common reasons are redundancy and load balancing. The etherchannel-group [number] mode on command in interface configuration mode adds the interface to the specified EtherChannel group. A switch can have six EtherChannels. An EtherChannel can have up to 8 ports.